Pedal powered vehicles are well known. Although bicycles are the most common, unicycles, tricycles, and quadricycles have all been built in the past. Such vehicles are currently used for physical fitness, recreation, and transportation.
Concerns about both the price of gasoline, as well as the environment, are expected to result in increased interest in the use of pedal powered vehicles for transportation. Although presently available bicycles are safe and easy to ride on a relatively dry road, slippery conditions such as snow, ice, rain, mud, or gravel can greatly increase the likelihood of a fall. A fall that occurs in traffic could potentially have serious consequences.
A quadricycle would be much safer in slippery conditions than a bicycle. However, when traveling over uneven surfaces, a presently available quadricycle, which typically includes rigid axles, would be unable to maintain contact between all four wheels and the ground at all times. Accordingly, there is a need for a means of maintaining contact between all four wheels of a quadricycle and the ground at all times.
Furthermore, a bicycle has the advantage of steering not only by turning the handlebars, but also by leaning into a turn. Leaning into a turn resists the centrifugal forces which would otherwise tend to cause a vehicle to tip over during a turn. Unfortunately, presently available quadricycles do not provide any means of leaning into a turn.
U.S. Pat. No. 4,360,224 discloses a tricycle having two front wheels and a single rear wheel. The front wheels are connected to the frame through a double wishbone suspension having a pair of upper arms and a pair of lower arms connected by vertical links at their outer ends. The upper arms are pivotally connected to the frame. The lower arms are pivotally connected to a longitudinal shaft by a shock absorbing cushion.
U.S. Pat. No. 6,286,846 discloses a suspension system for isolating a load independently from two separate inputs such as a pair of wheels. The suspension is applicable to two wheeled vehicles, with the inputs being the front and rear wheels of a bicycle.
US 2002/0190494, filed by C. Cocco et al. and published on Dec. 19, 2002, discloses a tricycle having two front wheels and a single rear wheel. The suspension assembly disclosed therein utilizes essentially vertical shock absorbers, within a relatively narrow structure.
A suspension system for a quadricycle is disclosed within US 2007/0029751, filed by M. Marcacci and published on Feb. 8, 2007. This suspension system is designed specifically to avoid steering caused by the rolling of the vehicle, as stated in paragraph [0026], [0029], and [0039] of Marcacci. Conversely, the present inventor believes that utilizing the leaning of the vehicle to affect or assist with steering is advantageous. Furthermore, this suspension system utilizes essentially vertical shock absorbers.
Accordingly, there is a need for a pedal powered vehicle having a suspension system which will permit leaning into a turn while negotiating a curve, while at the same time resisting excessive leaning of the vehicle.